Wiper bearing

ABSTRACT

The invention relates to a wiper bearing for a windshield wiper system comprising a bearing housing ( 12 ) provided with an outer tube forming the bearing housing ( 12 ) and an inner tube ( 24 ) arranged in a concentric manner in relation thereto and a journal ( 30 ) arranged on a bearing area ( 14 ) on the bearing housing ( 12 ) for receiving a tubular plate ( 40 ). It is proposed that an annular element ( 16 ), which is arranged in a coaxial manner on the journal ( 30 ), be provided outside the journal ( 30 ) in the region of the front side thereof ( 36 ).

BACKGROUND OF THE INVENTION

The invention starts with a wiper bearing.

A wiper bearing housing is used to support a wiper shaft and to positiona wiper axis as well as fastening receptacles for assembly in a vehicle.High forces and moments occur above all in the transition area betweenthe wiper bearing housing and the tubular plate, particularly in thecase of snow load or cases of lock-up.

A wiper system is known from DE 199 25 292 A1 in which the tubular platein the transition area has an enlarged cross section, which reduces thespecific load in the critical transition area and increases flexuralstrength and resistance to torsion.

SUMMARY OF THE INVENTION

In the case of a wiper bearing in accordance with the invention, it isproposed that an annular element that is arranged in a coaxial manner onthe journal be provided outside a journal that is provided to receive atubular plate. The journal is permanently connected to an outer tube ofthe wiper bearing forming the bearing housing or to an inner tubearranged in a concentric manner in relation thereto. Due to a positivelyengaged connection of the tubular plate with the journal, forces aretransferred from the bearing housing to the journal including torsionalforces. The journal henceforth assumes mainly tensile forces,compressive forces and torsional forces. The annular element and itsconnecting braces assume bending moments and bending forces. The journalis mechanically stressed less and more uniformly as a whole. The annularelement can essentially assume bending forces, which act in a plane,which is formed of a bearing axis and the journal. The tubular plate issupported by the annular element and the journal is relievedcorrespondingly. Only slight bending loads occur on the journal itself.It is also possible to provide two coaxially arranged annular elements.In this case, the outer annular element has very good stability andeases the connection of the tubular plate with the journal. Theconstruction is especially compact when the journal is fastened to theinner tube. The initiation of force in this case takes place on both theinner tube as well as on the outer tube.

Because of the low stress, a transitional geometry between the journaland its bearing point on the bearing housing can be designed simply witha shortened distance between a connecting area between the journal andthe tubular plate and the bearing area of the journal on the inner tubeor outer tube of the bearing housing. The wiper bearing, in particular awiper bearing made of plastic, can be designed to be shorter and morecompact than previous plastic wiper bearings in which attention had tobe paid to a long and harmonic transitional area in order to reduce anymechanical tension spikes occurring there. Because of the compact designof the wiper bearing, the tubular plate can be brought closer to thebearing area of the wiper axis, thereby resulting in a more rigidoverall system. Because of the uniform mechanical stress of the bearinghousing, it can be designed in a uniformly thin-walled manner, which isespecially advantageous for a wiper bearing design of plastic in orderto avoid bubbles forming in the plastic during manufacturing. Inaddition, a shorter cooling and cycle time during manufacturing is madepossible. In connection with the reduced dead weight, the wiper bearingwith the annular element can be cost-effectively manufactured andmounted. The tubular plate can be designed with a small cross section,which signifies a reduction in weight and a lower requirement forconstruction space. Because of elastic deformation, for example in thecase of a lock-up, wiper supports with a smaller cross section of thetubular plate relieve all components of the wiper system, even the wiperlever, thereby making possible additional cost savings since thesecomponents can be designed more simply.

Because of the arrangement of the annular element and the improvedsupport of the tubular plate in the bearing area, less movement occurswhen operating the wiper system and even in the case of high loads theconnecting point will not fail. The alignment of the wiper shaft remainspractically unchanged so that, according to the design, the adjustmentangle of the wiper blade to the vehicle window is retained, therebyguaranteeing good wiping quality.

Because of the special geometry, high component rigidity as well as animprovement in the rigidity of the overall system is achieved despitethe preferred use of unreinforced plastics for the wiper bearing. As aresult, the scope of use of wiper drives with plastic wiper bearings canbe expanded.

The bearing housing is resistance to bending and nevertheless can bemanufactured of unreinforced, cost-effective materials. Duringmanufacturing, work can be done with very simple sliders. Because of thedesign of the wiper bearing and the resulting tool structure, inaddition to unreinforced plastics, materials that cannot be demolded soeasily are also suitable in principle, such as reinforced plastics ormetallic diecasting materials, particularly Zn, Mg and Al.

The annular element is arranged connectionless to the journal on thebearing housing and can therefore keep the bending load away from thejournal to a large extent. In addition the annular element is fastenedwith braces on the bearing housing, via which the journal is accessiblefrom the outside at least in a connecting area, in which the tubularplate is connected to the journal. For one, the preferred fastening withupper and lower braces makes high rigidity of the annular element/bracearrangement possible, and, secondly, both manufacturing of the wiperbearing and connecting the tubular plate to the journal are simplifiedsince the journal is accessible from outside in a simple manner forcorresponding tools, for example crimping tools.

If the annular element is arranged axially in front of the journal, inparticular without overlapping with the journal on its front side, thewiper bearing can be manufactured with an advantageous tool without anannular core and a correspondingly simple and solid tool slider. Thisalso makes better tool cooling and core cooling possible with apreferred diecasting or injection molding method. If the journalprojects with a front side into the annular element, demolding of hollowprofile cores and of the annular core can be accomplished in the samedirection, requiring only a single tool slider.

If the journal is arranged approximately centric with respect to anaxial extension of the bearing housing, the annular element is supportedbroadly on the bearing housing and only slight component distortionoccurs during cooling after manufacture, which goes hand in hand withhigh geometry quality and good processsability. Alternatively, thejournal can be arranged off-center with respect to an axial extension ofthe bearing housing, e.g., on a lower end of the bearing housing. As aresult, broad support on the bearing housing is possible.

The wiper bearing can be designed to be especially rigid if the journalhas a cross section embodied as a hollow profile. This embodiment isespecially rigid. The tool cores required for this hollow profile can bealigned in such a way that they are pulled in the direction of thejournal, i.e., simultaneously with an annular tool core for generatingthe annular element. Alternatively, the journal has a cross sectionembodied as a T-support or a double T-support.

A connecting geometry can be created and demolded in two tool halves.The tool structure is especially simple.

It is advantageous if a component geometry between the annular elementand the bearing point can be demolded laterally during its manufacture.In addition to the simplifications of the tools already described, thismakes it possible for the tubular plate to be surrounded after beingslipped on in order to connect the tubular plate to the journal withpreferred so-called crimping. This guarantees good positive engagementand a qualitatively high quality of the connection between the tubularplate and the journal. In doing so, the tubular plate is deformedplastically and displaced into pockets of the wiper bearing housing orof the journal provided for this purpose. Standard tools for crimpingcan be used.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in greater detail in an exemplaryembodiment on the basis of the associated drawings. The drawings show:

FIG. 1 A wiper bearing with a short annular element with asymmetricalfastening via support profiles;

FIG. 2 A wiper bearing with a short annular element with symmetricalfastening with a hollow profile cross section;

FIGS. 3 a, b A depiction of sectional planes in the longitudinaldirection (a) and perpendicular to a journal line of symmetry (b);

FIGS. 4 a, b A tool structure and the separation of tool halves with across section with a hollow profile (a) and a cross section with aT-support profile (b);

FIGS. 5 a, b A tool structure (a) and a tool core with an annular core(b);

FIG. 6 A cross section through a wiper bearing with overlapping of thejournal and annular element;

FIGS. 7 a, b A tool structure (a) and a tool core without an annularcore (b);

FIG. 8 A cross section through a wiper bearing without overlapping ofthe journal and annular element;

FIGS. 9 a-f On the basis of a cross section through the journal, aprocedural sequence of a crimping process before (a) and after attachinga tubular plate (b), introduction of the tool (c), surrounding of thetubular plate with the tool (d), insertion of the die in the connectingarea between the tubular plate and the journal (e) and the completedconnection (f);

FIGS. 10 a, b A size comparison of a preferred wiper bearing (a) with aknown wiper bearing (b);

FIG. 11 A section through a wiper bearing with an annular elementexecuted as a double ring;

FIG. 12 A depiction of an assembly of wiper bearing and tubular plate;

FIG. 13 A comparison of component rigidities of a preferred wiperbearing in accordance with the invention and two known wiper bearingswith a hollow profile journal and a T-support journal.

DETAILED DESCRIPTION

The invention is particularly suitable for wiper bearings made ofplastic. In general, the same reference numbers are used in the figuresfor the same parts.

FIG. 1 shows a wiper bearing 10 for a windshield wiper system with abearing housing 12 and a journal 30 arranged on a bearing area 14 on abearing housing 12 and a short annular element 16. The bearing housing12 formed by an outer tube concentrically surrounds an inner tube 24.The short annular element 16 is arranged coaxially outside the journal30 in the area of its front side 36. The journal 30 and the annularelement 16 are arranged off-center with respect to an axial extension ofthe bearing housing 12.

The annular element 16 is fastened on the bearing housing 12 with anupper brace 18 and a lower brace 20, through which the journal 30 isaccessible from the outside at least in a connecting area 32. A tubularplate (not shown) will subsequently be connected to the journal 30 inthis connecting area 32. The braces 18, 20 are embodied in this case asT-supports. The annular element 16 has no direct connection to thejournal 30 so that the tubular plate (not shown) can be slipped on thejournal 30 in a small free space between the journal 30 and the innercircumference of the annular element 16. The free space is dimensionedin such a way that the tubular plate can be adjacent to both the journal30 as well as the inner circumference of the annular element 16.

FIG. 2 shows a wiper bearing 10 with a short annular element 16 with asymmetrical connection of the journal 30 and the annular element 16 onthe bearing housing 12. The lower and upper braces 18, 20, which holdthe annular element 16, have a hollow profile cross section. The journal30 and the annular element 16 are arranged approximately centric withrespect to an axial extension of the bearing housing 12.

FIGS. 3 a, b depict a representation of sectional planes through thewiper bearing 10. FIG. 3 a shows a section in the longitudinal directionof the journal 30. It is evident that the journal 30 is connectionlessto the annular element 16. FIG. 3 b shows a section perpendicular to ajournal line of symmetry. The journal 30 has a hollow profile, which hasa reinforcing element arranged centrically; the lower and upper braces18, 20, which hold the annular element 16, are also embodied as hollowprofiles.

FIGS. 4 a, b show a cross section of a preferred tool for manufacturingbraces 18, 20 and the journal 30 as well as the separation of toolhalves 50, 52 of the tool. The arrangement of the braces 18, 20 and ofthe journal 30 in accordance with the invention advantageously permitsthe use of a tool, which can be divided in the center into the two toolhalves 50, 52. FIG. 4 a shows the tool with braces 18, 20 embodied ashollow profiles and a journal 30 embodied as a hollow profile. FIG. 4 bshows a variation of the tool for braces 18, 20 embodied as a T-profileand the journal 30.

FIGS. 5 a, b show as longitudinal section through a preferred toolstructure of a tool 60 (FIG. 5 a) and an associated preferred toolslider 62 (FIG. 5 b) for an embodiment of the journal 30 and braces 18,20 with hollow profiles. In order to demold the four hollow profilecores, as shown in FIG. 4 a for example, only a single tool slider 62 isadvantageously required, whereby the annular core 64 and the hollowprofile cores can be demolded in this same direction. The annular core64 is required if the journal 30 and annular element 16 overlap, i.e.,the front side 36 of the journal 30 projects into the annular element16. FIG. 6 shows a section through this type of wiper bearing 10 withoverlapping of the journal 30 and the annular element 16 with a tubularplate 40 slid on. The tubular plate 40 is stably clamped between theannular element 16 and journal 30 in the overlapping area.

FIGS. 7 a, b depict a tool structure without an annular core. The toolstructure of the tool 70 shows a mold for a shorter journal 30 than inFIG. 5 a (FIG. 7 a) and a tool core without an annular core (FIG. 7 b).A solid tool slider structure is possible as a result; moreover the tooland the tool core can be cooled better. The variation of this type ofwiper bearing 10 is depicted in FIG. 8 as a cross section. A tubularplate 40 is slid onto a journal 30 and is simultaneously encircled by anannular element 16. The journal 30 is shorter than in the exemplaryembodiment in FIG. 6 and does not project into the annular element 16,which sits axially in front of the journal 30.

FIGS. 9 a-f illustrate on the basis of cross sections through thejournal 30 and the braces 18, 20 a procedural sequence of a connectingprocess between the journal 30 and the tubular plate 40 that is executedas a crimping process. FIG. 9 a shows the journal 30 and braces 18, 20at the beginning of connection. FIG. 9 b also shows the tubular plate 40that is slid onto the journal 30. Finally, on both sides of the journal30, a tool part 70, 72 with die pairs 74, 76 each approaches the journal30 (FIG. 9 c) until the journal 30 that is surrounded by the tubularplate 40 is surrounded by the tool parts 70, 72 (FIG. 9 d). This ispossible because of the special wiper bearing geometry and veryadvantageous for the quality of the connection between the journal 30and the tubular plate 40. Finally, the die pairs 74, 76 for creating apositive engagement between the wiper bearing or the journal 30 and thetubular plate 40 are pressed into the tubular plate 40. The die pairs74, 76 displace the tubular material into pockets on the journal 30provided for this purpose (FIG. 9 e). FIG. 9 f shows the finishedarrangement upon conclusion of the connecting process. The tubular plate40 is connected with positive engagement to the journal 30 in theconnecting area (corresponding to connecting area 32 in FIG. 1 and FIG.2).

FIGS. 10 a, b depict a size comparison of a preferred wiper bearing 10(FIG. 10 a) with a known wiper bearing 80 (FIG. 10 b). The preferredwiper bearing 10 has a journal 30, which is fastened on an inner tube 24of the wiper bearing 10 so that an initiation of force occurs both onthe inner tube 24 as well as on the bearing housing 12 embodied as theouter tube. The bearing area 26 of the journal 30 and the bearing area28 of the annular element 16 or of the elements on the inner tube 24holding the annular element 16 are preferably embodied concentrically inorder to guarantee good roundness of the two bearing areas 26, 28. Onthe other hand, the known wiper bearing 80 shows a journal 82 that mustbe considerably longer than is the case with the arrangement inaccordance with the invention with correspondingly lower flexuralstrength and tension excesses under load.

FIG. 11 shows a section through a wiper bearing 10, in which the annularelement 16 is embodied as a double ring. The double ring increases thestability of the annular element 16. In addition, this creates a greaterfree space between the journal 30 and the braces 18, 20 so that whenconnecting the tubular plate 40 to the journal 30 there is more spacefor a tool, particularly a crimping tool.

FIG. 12 shows a depiction of an assembly of wiper bearing 10 and tubularplate 40. The tubular plate 40 is connected with positive engagement tothe journal 30 in the connecting area 32. Braces 18, 20 hold an annularelement 16, which encircles the tubular plate 40. The braces 18, 20 areembodied as hollow profiles.

The embodiment in accordance with the invention of a wiper bearing 10provides a clear improvement in component rigidity. FIG. 13 shows acomparison of component rigidities of a preferred wiper bearing 10 andtwo known wiper bearings with a hollow profile journal and a T-supportjournal similar to the design in FIG. 10 b.

The known wiper bearing with the T-support journal has the lowestcomponent rigidity, which is clearly evident in Curve C. Even though aknown wiper bearing with a hollow profile journal shows an improvementin the component rigidity (Curve B), the wiper bearing 10 in accordancewith the invention is improved in terms of its component rigidity bymore than a factor of 2. This is due to the fact that the distributionof the elastic tension in this case is very uniformly distributed on thejournal, while in the case of the known wiper bearings local tensionexcesses occur as analyses using the finite element method (FEM) haveshown.

1. Wiper bearing for a windshield wiper system comprising a bearinghousing (12) provided with an outer tube forming the bearing housing(12) and an inner tube (24) arranged in a concentric manner in relationthereto and a journal (30) arranged on a bearing area (14) on thebearing housing (12) for receiving a tubular plate (40), characterizedin that an annular element (16), which is arranged in a coaxial manneron the journal (30), is provided outside the journal (30) in the regionof the front side thereof (36).
 2. Wiper bearing according to claim 1,characterized in that the annular element (16) is arrangedconnectionless to the journal (30) on the bearing housing (12).
 3. Wiperbearing according to claim 1, characterized in that the annular element(16) is fastened with braces (18, 20) on the bearing housing (12), viawhich the journal (30) is accessible from the outside at least in aconnecting area (32).
 4. Wiper bearing according to claim 1,characterized in that the annular element (16) is arranged axially infront of the journal (30).
 5. Wiper bearing according to claim 4,characterized in that the journal (30) projects with the front side (36)into the annular element (16).
 6. Wiper bearing according to claim 1,characterized in that the journal (30) is arranged approximately centricwith respect to an axial extension of the bearing housing (12).
 7. Wiperbearing according to claim 1, characterized in that the journal (30) isarranged off-center with respect to an axial extension of the bearinghousing (12).
 8. Wiper bearing according to claim 1, characterized inthat the journal (30) is fastened to the inner tube (24).
 9. Wiperbearing according to claim 1, characterized in that the journal (30) hasa cross section embodied as a hollow profile.
 10. Wiper bearingaccording to claim 1, characterized in that the journal (30) has a crosssection embodied as a double T-support.
 11. Wiper bearing according toclaim 1, characterized in that a component geometry between the annularelement (16) and the bearing area (14) can be demolded laterally duringits manufacture.
 12. Wiper bearing according to claim 2, characterizedin that the annular element (16) is fastened with braces (18, 20) on thebearing housing (12), via which the journal (30) is accessible from theoutside at least in a connecting area (32).
 13. Wiper bearing accordingto claim 2, characterized in that the annular element (16) is arrangedaxially in front of the journal (30).
 14. Wiper bearing according toclaim 5, characterized in that the journal (30) is arrangedapproximately centric with respect to an axial extension of the bearinghousing (12).
 15. Wiper bearing according to claim 5, characterized inthat the journal (30) is arranged off-center with respect to an axialextension of the bearing housing (12).
 16. Wiper bearing according toclaim 7, characterized in that the journal (30) is fastened to the innertube (24).
 17. Wiper bearing according to claim 8, characterized in thatthe journal (30) has a cross section embodied as a hollow profile. 18.Wiper bearing according to claim 9, characterized in that a componentgeometry between the annular element (16) and the bearing area (14) canbe demolded laterally during its manufacture.